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Elliptio complanate mold of fresh water, one of the two species used in the experimentCREDIT: Westcott Phillip
According to researchers at Penn State and Union College, elevated concentrations of strontium, an element badociated with oil and gas sewage, have accumulated in the shells of freshwater mussels downstream of watersheds. disposal of fracking wastewater.
"Freshwater mussels filter the water and when they develop a hard shell, the shell material registers some of the quality of the water over time," he said. Nathaniel Warner, badistant professor of environmental engineering at Penn State. "Like dark circles, you can count the seasons and years in their shell and have a good idea of the quality and chemical composition of the water for specific periods."
In 2011, it was discovered that despite the treatment, water and sediment downstream of the fracking wastewater disposal sites still contained fracking chemicals and had become radioactive. In turn, drinking water was contaminated and aquatic life, such as the freshwater mussel, was dying. In response, Pennsylvania has asked sewage treatment plants not to treat or discharge water from unconventional oil and gas drilling, such as Marcellus shale. As a result, the industry has turned to recycling most of its wastewater. However, researchers are still discovering the long-term effects, especially during the three-year boom that took place between 2008 and 2011, when more than 2.9 billion liters of wastewater were released into the Pennsylvania water course.
"Freshwater pollution is a major concern for ecological and human health," said David Gillikin, professor of geology at Union College and co-author of the study. "It is important to develop ways to retroactively document this pollution in order to shed light on what is happening in our waterways."
The researchers began by collecting freshwater mussels from the Alleghany River, 100 meters upstream and one kilometer downstream of a sewage disposal facility licensed by the national system. Elimination of pollutant releases, in Warren, Pennsylvania, as well as mussels from two other rivers – the Juniata and Delaware – for which no spill of oil and gas had been reported.
Once at the laboratory, they dissected the shell and then drilled and collected the shell powder layer by layer to look for isotopes of two elements: oxygen, used to determine the year and the season, and strontium, both bearing a distinctive signature. of the rock formation where they were produced. The results were recently published in Science and technology of the environment.
The team found significantly elevated strontium concentrations in the shells of freshwater mussels collected downstream of the facility, while the shells collected upstream and in the Juniata and Delaware rivers did not show up. that little variability and no trend over time.
Surprisingly, the amount of strontium found in shell layers created after 2011 does not show an immediate reduction of contaminants. Instead, the change appeared more gradually. This suggests that sediments where freshwater mussels live may still contain higher concentrations of heavy metals and other chemicals used in unconventional drilling. "We know that the development of Marcellus has affected downstream sediments for tens of kilometers," Warner said. "And it looks like it could still be affected for a long time.The short time we have allowed to dump this waste could leave a long legacy."
According to the US Department of Energy, nearly 95% of new wells drilled today are hydraulically fractured, accounting for two-thirds of total US marketed natural gas production and about half of crude oil production American.
"The wells are growing, they are using more water, they are producing more wastewater and this water has to go somewhere," said Warner. "Making the right choices about how to handle this water will become vital."
Warner added that there was not much difference between conventional and unconventional wastewater from the point of view of pollution. He said high levels of contaminants of strontium, sodium, chloride and other contaminants are still present in conventional oil and gas development.
Now that researchers know that freshwater mussels can be used as chemical recorders of fracking pollutants in waterways, they would like to look at the soft tissues of freshwater mussels, since muskrats and the fish feed on it. They also hope to expand their research to other specific pollutants that are likely to bioaccumulate in surface water disposal areas.
"We want to see what metals the mold incorporates predictably and which ones are not," said Thomas Geeza, PhD student in environmental engineering at Penn State and co-author of the study. "We are trying to develop this as a tool that can be used in other water courses to answer other questions."
The molds could also be used to study possible infiltrations in the facilities.
"We checked to see if wastewater treatment plant wastewater discharges were stored in tanks, but we could also imagine using this technique to look for leaks from retention ponds or accidental releases in water courses close to fracking, "said Gillikin.
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